Low-Silver Solder Alloy Composition for Void Suppression
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Solution Overview
Problem
Existing low silver tin-silver-copper solder alloys face challenges with insufficient wettability and void suppression, particularly when reducing silver content to lower costs, which affects fatigue resistance and connection reliability in electronic circuit boards.
Innovation Solution
A solder alloy with a silver content of 0.05-0.2 mass% and a composition of tin, silver, copper, nickel, antimony, and indium, with no germanium, optimized to ensure excellent wettability, fatigue resistance, and void suppression, is developed, along with a solder paste formulation for electronic circuit boards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silver content is reduced to lower costs, then cost decreases, but fatigue resistance and wettability deteriorate
Solution Approach 1:
The patent changes the compositional parameters by precisely controlling silver content within 0.05-0.2 mass% and establishing specific ranges for copper (0.1-1.0 mass%), nickel (0.01-0.5 mass%), antimony (0.01-2.0 mass%), and indium (0.003-0.03 mass%). This parameter optimization resolves the contradiction by finding the optimal balance point where minimal silver content still achieves adequate fatigue resistance and wettability.
Solution Approach 2:
The patent creates a composite solder alloy system combining tin with multiple elements (silver, copper, nickel, antimony, indium) in specific proportions. This composite approach allows the synergistic interaction of different elements to compensate for reduced silver content, maintaining fatigue resistance and wettability while lowering overall cost.
2Quantity of substance
If silver content is reduced to lower costs, then cost decreases, but wettability deteriorates
Solution Approach 1:
The patent optimizes compositional parameters by setting silver content at 0.05-0.2 mass% and coordinating with specific amounts of other elements, particularly copper (0.1-1.0 mass%) and nickel (0.01-0.5 mass%), to maintain adequate wettability despite reduced silver content.
Solution Approach 2:
The patent introduces intermediary elements (copper, nickel, antimony, indium) that mediate the wettability function when silver is reduced. These intermediary elements compensate for the reduced surface activity provided by silver, ensuring adequate wettability is maintained through their combined effect.
3Object-affected harmful factors
If germanium is added to improve certain properties, then oxidation resistance improves, but void generation increases due to easy oxidation
Solution Approach 1:
The patent extracts germanium from the alloy composition entirely, setting germanium content at 0 mass%. This elimination removes the source of oxidation-related void generation while the patent achieves oxidation resistance through protective flux coatings and controlled atmosphere processing instead.
Solution Approach 2:
The patent replaces permanent oxidation resistance from germanium addition with a disposable protective approach using flux coatings that consume during soldering to protect the alloy surface, preventing oxidation without introducing void-forming elements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves low costs, improved wettability, and suppressed void generation, ensuring excellent bonding strength, impact resistance, and fatigue resistance in electronic circuit boards, while maintaining cost-effectiveness.
Implementation Method 1
a solder alloy containing, for example, 0.05 to 2.0 mass% of silver, 1.0 mass% or less of copper, 3.0 mass% or less of antimony, 2.0 mass% or less of bismuth, 4.0 mass% or less of indium
Implementation Method 2
contains tin, silver, copper, nickel, antimony, bismuth, and indium as essential components
Data Source
AI summary
A solder alloy is a tin-silver-copper solder alloy containing tin, silver, copper, nickel, antimony, bismuth, and indium, and substantially does not contain germanium, wherein relative to the total amount of the solder alloy, the silver content is more than 0.05 mass% and less than 0.2 mass%, and the antimony content is 0.01 mass% or more and less than 2.5 mass%.